1. Field of the Invention
The present invention relates to an automatic cord rewinding apparatus for unwinding and unrewinding an electric cord for supplying electric instruments with electric power, and more particularly to an automatic cord rewinding apparatus provided with contacts for connecting the electric power to said electric instruments regardless of the rotation of the winding wheel of the rewinding apparatus.
2. Description of the Prior Art
Conventionally, a known automatic electric cord rewinding apparatus comprises, as shown in FIGS. 1 and 2, a housing 1, a winding wheel 3 on which the electric cord 2 is wound and which is rotatably connected to said housing 1, a coiled torsion spring 4 disposed between said winding wheel 3 and said housing 1 such that the outer end of said spring 4 is connected to the boss of said wheel 3 but the inner end thereof is connected to said housing 1. The spring 4 is adapted for biasing the winding wheel 3, and a spring cover 5 for protecting said cord rewinding apparatus (hereinafter, referred to simply as "the rewinding apparatus") from the outside shock.
Thus, upon removing the pulling force for the cord 2 after having unwound the electric cord 2 from the winding wheel 3, the rewinding apparatus will automatically rewind said cord 2 on the winding wheel 3 by the rotation of said winding wheel 3 caused by the restoring force of the torsion spring 4.
To restrain the abrupt rewinding of the cord, the rewinding apparatus is provided with a stop lever 7 having a rubber ring 6. The stop lever 7 is mounted to the housing 1. Thus, the reversed rotation of the winding wheel 3, caused by the restoring force of the torsion spring 4, is prevented as a result of contact of the rubber ring 6 with the winding wheel 3, thereby accomplishing the prevention of the abrupt rewinding of the cord 2 during the unwinding state of the cord 2.
In addition, the rewinding apparatus has to be provided with contacts through which the outside electric power is connected to the electric instrument to which said rewinding apparatus is provided.
The known rewinding apparatus is, therefore, provided with a cap 8 of an insulation material as shown in FIGS. 1 and 2A. The cap 8 has a pair of annular grooves 8a and 8b in which a conduction ring 9 or 10 is tightly received, respectively. In addition, the winding wheel 3 is provided with a center opening 3a formed at the inner side thereof facing the housing 1. The center opening 3a allows lead wires 2a of the electric cord 2 to extend outwards therethrough, said lead wires 2a connected to a pair of conduction rings 9 and 10 by soldering, respectively. The insulation cap 8 is thereafter mounted to the center opening 3a of the winding wheel 3 in order to accomplish the wheel assembly.
Also, the housing 1 is, as shown in FIGS. 1 and 2B, provided with a pair of spring type terminals 11 and 12 mounted to said housing 1 by means of rivets 13, respectively, said terminals 11 and 12 connected to power supply lead wires (not shown) of the electric instrument, thereby accomplishing the housing assembly.
Thus, upon mounting the outer end of the torsion spring 4 to the boss of the winding wheel 3, the other end thereof to the housing 1 and combining the wheel assembly of FIG. 2A and the housing assembly of FIG. 2B with each other by means of a combining shaft 14, the spring type terminal 11 is naturally connected to the relatively larger diameter conduction ring 9 while the other spring type terminal 12 is naturally connected to the relatively smaller diameter conduction ring 10. Therefore, there is provided contacts at respective connections between the conduction rings 9 and 10 and the spring type terminals 11 and 12 so that the electric power of said conduction rings 9 and 10 is always connected to said spring type terminals 11 and 12 through said contacts. Thus, the outside electric power front the plug 15 is supplied to the electric instrument regardless of the rotation of the winding wheel 3.
However, the known rewinding apparatus has a disadvantage in that the clearance in assembly therefor causes the contact resistance between the conduction rings 9 and 10 and corresponding spring type terminals 11 and 12 to be increased during the rotation of the winding wheel 3 that the contacts overheat. Also, there is another disadvantage in that a short may occur between the polar charging parts of the conduction rings 9 and 10 due to exchange of polar brass powder between said conduction rings 9 and 10, said polar brass powder is produced as a result of the frictional contact between the conduction rings 9 and 10 and the spring type terminals 11 and 12 generated during the rotation of the winding wheel 3 in accompanying with the rotation of the contacts. Furthermore, the rewinding apparatus has still another disadvantage in that it is provided with no means for protecting the lead wires 2a from an outside shock. This results in the movement of said lead wires 2a, so that the leas wires 2a are easily broken from the conduction rings 9 and 10 to which said wires 2a are connected by soldering.